The physical characteristics of small islands (limited land area, small plains, high exposure to
unpredictable climate variations and sea-related hazards) and their human characteristics (strong dependence on subsistence activities and ecosystems) explain their potentially high vulnerability to environmental changes (i.e., changes in the ocean and sea-related hazards). They have become symbolic of the threats associated with climate change: rising sea levels, increase in cyclone intensity and frequency, as well as ocean warming and acidification. Although a wide diversity of answers is to be expected from one island system to another, small islands are exposed to significant threats: reduction in their surface area, increase in coastal erosion, degradation of coral reefs and mangroves, etc. The impacts on land (soil, water, fauna and flora) and marine resources (reefs and fisheries) are major, jeopardizing the future of human survival on many islands. Consequently, island societies have to face an extremely pressing challenge.
Changes in the ocean and the cryosphere play a key role in the Earth’s climate. Both the regulation role and services provided by these ecosystems are under threat. The impacts of these changes on ecosystems and human societies are now obvious. They jeopardize the safety of the most exposed populations, especially in coastal areas, on small islands, on mountains and in polar regions, and have economic, social and cultural impacts on all human communities, including those living away from these areas. For the most vulnerable populations, environmental migration can be an answer. Anticipating and adapting to these changes would help to reduce impacts on natural environments and on the communities that depend on them.
For approximately 3 000 years, sea-level had been stable but recent observations indicated an increase in the average speed of sea-level rise, currently at 3.5 millimetres per year. The heat distribution in the climate system causes thermal expansion of oceans, continental glaciers melts and mass loss of ice caps, all evenly contributing to the phenomenon. If these processes intensify, recent estimates suggest a mean sea-level rise of 60 cm to 1 meter by 2100. Sea-level rise significantly varies from one region to another. Moreover, this process is further accentuated when combined with other non-climate factors such as soil compaction or loss of sediment supply by rivers… The impacts of sea-level rise are uncertain in many regions and the use of evolution models to address climate forcing is an important tool to help decision-making in urban planning.
Debates on mitigation and adaptation measures to adopt against climate change are based on observations and estimations over a range of less than 250 years. A recent study by Clark and his collaborators, published in Nature Climate Change, covers extremely long term (over 10,000 years1) climate consequences. Their scope is linked to CO2 emissions. According to these scenarios, the temperature increase could exceed the 2°C limit, and a 2 to 4 meters per century sea-level rise could be expected in the next millennium. These results confirm the importance of keeping a large quantity of fossil resources untouched.
Measurements from tide gauges and satellites have shown that the sea is rising globally at an average rate of about 1.7mm per year since the beginning of the 20th century, a direct conse- quence of human-driven global warming, although there is strong regional variability. This in- crease is mainly due to two factors: the increase in ocean temperature resulting in expansion of sea water, and the melting of continental ice sheets, glaciers and ice caps with an input of fresh water into the ocean. Despite uncertainties, proposed scenarios indicate that sea levels will continue to rise at a faster pace than during the 20th century, reaching an increase of more than 25cm (best case) and 82cm (worst case but likely underestimated) by 2100.
Since the 1990s, the Intergovernmental Panel on Climate Change (IPCC) has used global level analyses of vulnerability to inform investment and action against the effects of climate change. Beyond the IPCC, the practice has been used widely to understand the vulnerability of coastal areas to a variety of hazards, including climate change. These analyses, however, have been driven by objectives that change from one assessment to the next, with very different conceptualisations of vulnerability. Over time these analyses have become increasingly data intensive and complex, drawing from an ever-expanding number of indicators. Such variations in objectives, conceptualisations and data have led to different and often contradictory rankings of priority areas for climate change action. The increased complexity makes it more difficult to disentangle the root causes of these different rankings and the degree to which climate change influences vulnerability rankings, compared to other factors such as local environment factors and the adaptive capacity of populations to deal with environmental change. If these global indicator analyses were deconstructed, climate decision-makers could use them as scoping studies rather than expect them to provide comprehensive and robust priorities for investment. Such scoping studies, if they are to be truly useful to climate decision-makers, need to be simplified and harmonised to isolate climate change specific drivers. They can help target the locations for more in-depth local level analyses and should be supplemented by global level analyses of costs of climate action including technical, social and economic factors.
Kiribati archipelago mythology teaches us that the world began with a crack in a rock, followed by a mixture between dry and moist matter and finally by the prolific efflorescence of a crowd of creative ancestors. Scientific facts in the western world warn that within less than 300 years, these Eastern Micronesian atolls will disappear as a result of rising sea level due to global warming. Ethnographic fieldwork demonstrates how these people of Oceania, who settled in the heart of the Pacific more than a thousand years ago, have the dignity to interpret present climate instability with remarkable philosophical intelligence. Climate change reveals the reality of this duel between the survival of so-called modern progress that continues to endanger the future of the planet on one hand, and the survival of traditional ways of living with the belief that Man evolves in a respected natural environment on the other hand. These two confronting issues will be presented at the coming Climate Conference in Paris. Is it such a utopian concept to expect the decision-makers to offer a sacrifice to Mother Nature?